Receptacle technology, and in particular capsule technology, continues to be subject to development and improvements and so does the manufacture thereof, including processes and equipment. In its basic form, standard containers for pharmaceuticals or other powdered, granular or liquid substances (generally referred to as telescope-type or two-piece capsules) include a tubular-shaped and/or cylindrically-shaped first part, namely a cap part, which is closed on one end and open on the other opposite end. A tightly fitting second part of similar shape, namely the body part, is of smaller diameter than the cap part and is typically telescopically engaged therein to form the overall dosage form or two-piece capsule. Similar capsule technology may be used to generate multi-compartment capsules.
Capsules generally comprise or are made of functional base shell materials (most commonly gelatin, but in more recent times also alternate polymers such as celluloses or pullulan) and other additives such as gelling agents, plasticizers and/or colorants.
In particular colorants have been typically employed specifically to provide a vast sweet of color options for capsules and thus purely for providing an aesthetic appearance sometimes linked to the branding of the ultimate dosage form. Such colorants are commonly synthetically derived colorants or selectively extracted pigments from natural sources since typically such materials tend to experience lesser fading with time as well as particular resistance to thermal degradation.
Nevertheless, there is a desire for introduction of natural colorants in hard capsules, however this poses several challenges which have limited their use in favor of synthetically derived or extracted colorants and pigments.
There is a desire to provide hard capsule compositions that contain truly natural colorants that provide for good physical and color stability as well as added functionality and/or improved compatibility with aqueous based gelling systems used specifically in hard capsule manufacture.
There is further a desire for colorants that allow their incorporation in capsule making compositions without further dispersion prior to mixing therewith.